Bone age assessment in growing subjects is a well-known diagnostic tool that is especially useful in predicting stature and/or growth problems in children, teenagers and adults.
Many methods of assessing bone age are based upon radiographic analysis, such as the Greulich and Pyle (GP) method (Greulich W W, Pyle S I, Radiographic atlas of skeletal development of the hand and wrist, 2nd ed. Stanford Calif., Stanford University Press, 1959.) and the Tanner and Whitehouse (TW2) method [Tanner, J M, Whitehouse, R H, Marshall, W A, et al. “Assessment of skeletal maturity and prediction of adult height” (TW2 method). NY, Academic Press], both of which assess bone age by the radiographic presentation of the bones of the wrist and hand. In the Greulich and Pyle method a comparison is made between the child's radiograph and the corresponding standard in the Greulich and Pyle atlas. In the TW2 method 20 bones in hand and wrist are scored according to their stage, thus producing a total score for which a skeletal age may be read directly from the tables.
These methods present problems of accessibility as X-ray units are often available only in secondary care centers such as hospitals. Additionally, ionizing radiation is undesirable in elective procedures, especially to children.
Allessandro Castriota-Scanderbeg et al., in “Skeletal age assessment in children and young adults: Comparison between a newly developed sonographic method and conventional methods,” Skeletal Radiology 1998 27:271-277, propose a method for assessing skeletal age using ultrasound imaging measurements of the thickness of femoral head articular cartilage. In this method, a non-cartilage structure in an ultrasound image, an epiphysis, is linearly measured along a cross sectional plane without regard to structural aspects such as bone density. Further, this method is inaccurate and likely requires an imaging specialist for its administration, detracting from its cost-effectiveness.
Chalana et al. U.S. Pat. No. 5,605,155 uses ultrasound images for the measurement of fetal head structure to predict fetal head size. Hechard Patrick, FR 2768322 uses X-rays or ultrasound to measure the thickness of the epiphysis and metaphysis of a bone to establish an index used for assessing a “Ratio of Residual Growth.” Holmberg, U.S. Pat. No. 6,135,960 proposes using ultrasound transducers placed in a Cartesian coordinate system for characterizing objects within the body. The above publications assess object boundaries utilizing dimensional ultrasound imaging techniques without regard to structural aspects such as bone density.
Ultrasonic methods of bone density measurement are known. For instance, according to prior art ultrasound measurement systems, (for example, WO 00/28316 and U.S. Pat. No. 5,564,423, the disclosure of which are incorporated herein by reference), ultrasound is used to determine the density of a non-cartilage osseous structure.
Thus use of backscatter attenuation to determine bone density is described by Wear, K A and Garra, B S, “Assessment of bone density using ultrasonic backscatter”, Ultrasound Med Biol, 1998 June; 24(5):689-95.
Langton, et al. in “Quantitative Ultrasound” Chapter 17, p. 311-312, measure bone's speed of sound and broadband ultrasound attenuation in children using the center of the posterior portion of the Calcaneal, specifically so the ultrasound signal does not pass through the Calcaneal growth plate. This measurement area begins ossification prenatally so that this method estimates bone's speed of sound and broadband ultrasound attenuation based upon non-cartilage properties.